1. Field of the Invention
This invention relates to an improved process of preparing an alkylpolyglycoside by the reaction of a saccharide and a higher alcohol in the presence of an acid catalyst and particularly to the removal of the excess alcohol from the reaction product.
2. Statement of Related Art
Alkylglycosides are conveniently prepared by reacting an alcohol of the type and chain length which is desired to form the "alkyl" portion of the glycoside of interest with a saccharide reactant. Typically such reaction is conducted at an elevated temperature and in the presence of an acid catalyst. Various alkylglycoside products and processes for making same are disclosed in a variety of representative patents. U.S. Pat. No. 4,987,225 contains an extensive listing of processes for preparing alkylglycoside compositions. Included therein is U.S. Pat. No. 4,393,203 to Mao et al. (issued Jul. 12, 1983) which includes the step of removal of the excess alcohol in a thin film evaporator. U.S. Pat. No. 5,079,350 further describes a method for removing unreacted alcohol from the glycoside surfactant product by contacting the alkylglycoside and alcohol mixture with a sparging stream of inert gas under reduced pressure in a thin film evaporator maintained at a temperature in the range of about 140.degree. C. up to 200.degree. C. The process is described as substantially removing all of the unreacted alcohol and the odor from the glycoside product. At temperatures above 200.degree. C., i.e., 210.degree. C., the color (hue) of the alkylglycoside is described as noticeably deteriorated.